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http://journals.lww.com/acsm-msse/Fulltext/2016/03000/Nutrition_and_Athletic_Performance.25.aspx
ABSTRACT: It is the position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine that the performance of, and recovery from, sporting activities are enhanced by well-chosen nutrition strategies. These organizations provide guidelines for the appropriate type, amount, and timing of intake of food, fluids, and supplements to promote optimal health and performance across different scenarios of training and competitive sport. This position paper was prepared for members of the Academy of Nutrition and Dietetics, Dietitians of Canada (DC), and American College of Sports Medicine (ACSM), other professional associations, government agencies, industry, and the public. It outlines the Academy’s, DC’s and ACSM’s stance on nutrition factors that have been determined to influence athletic performance and emerging trends in the field of sports nutrition. Athletes should be referred to a registered dietitian/nutritionist for a personalized nutrition plan. In the United States and in Canada, the Certified Specialist in Sports Dietetics (CSSD) is a registered dietitian/nutritionist and a credentialed sports nutrition expert.]]>Tue, 01 Mar 2016 00:00:00 GMT-06:0000005768-201603000-00025http://journals.lww.com/acsm-msse/Fulltext/2015/11000/Updating_ACSM_s_Recommendations_for_Exercise.28.aspx
ABSTRACT: The purpose of the American College of Sports Medicine’s (ACSM) exercise preparticipation health screening process is to identify individuals who may be at elevated risk for exercise-related sudden cardiac death and/or acute myocardial infarction. Recent studies have suggested that using the current ACSM exercise preparticipation health screening guidelines can result in excessive physician referrals, possibly creating a barrier to exercise participation. In addition, there is considerable evidence that exercise is safe for most people and has many associated health and fitness benefits; exercise-related cardiovascular events are often preceded by warning signs/symptoms; and the cardiovascular risks associated with exercise lessen as individuals become more physically active/fit. Consequently, a scientific roundtable was convened by the ACSM in June 2014 to evaluate the current exercise preparticipation health screening recommendations. The roundtable proposed a new evidence-informed model for exercise preparticipation health screening on the basis of three factors: 1) the individual’s current level of physical activity, 2) presence of signs or symptoms and/or known cardiovascular, metabolic, or renal disease, and 3) desired exercise intensity, as these variables have been identified as risk modulators of exercise-related cardiovascular events. Identifying cardiovascular disease risk factors remains an important objective of overall disease prevention and management, but risk factor profiling is no longer included in the exercise preparticipation health screening process. The new ACSM exercise preparticipation health screening recommendations reduce possible unnecessary barriers to adopting and maintaining a regular exercise program, a lifestyle of habitual physical activity, or both, and thereby emphasize the important public health message that regular physical activity is important for all individuals.]]>Sun, 01 Nov 2015 00:00:00 GMT-05:0000005768-201511000-00028http://journals.lww.com/acsm-msse/Fulltext/2016/06000/Physical_Activity,_Fitness,_Cognitive_Function,.27.aspx
Background: The relationship among physical activity (PA), fitness, cognitive function, and academic achievement in children is receiving considerable attention. The utility of PA to improve cognition and academic achievement is promising but uncertain; thus, this position stand will provide clarity from the available science.
Objective: The purpose of this study was to answer the following questions: 1) among children age 5–13 yr, do PA and physical fitness influence cognition, learning, brain structure, and brain function? 2) Among children age 5–13 yr, do PA, physical education (PE), and sports programs influence standardized achievement test performance and concentration/attention?
Study Eligibility Criteria: This study used primary source articles published in English in peer-reviewed journals. Articles that presented data on, PA, fitness, or PE/sport participation and cognition, learning, brain function/structure, academic achievement, or concentration/attention were included.
Data Sources: Two separate searches were performed to identify studies that focused on 1) cognition, learning, brain structure, and brain function and 2) standardized achievement test performance and concentration/attention. PubMed, ERIC, PsychInfo, SportDiscus, Scopus, Web of Science, Academic Search Premier, and Embase were searched (January 1990–September 2014) for studies that met inclusion criteria. Sixty-four studies met inclusion criteria for the first search (cognition/learning/brain), and 73 studies met inclusion criteria for the second search (academic achievement/concentration).
Study Appraisal and Synthesis Methods: Articles were grouped by study design as cross-sectional, longitudinal, acute, or intervention trials. Considerable heterogeneity existed for several important study parameters; therefore, results were synthesized and presented by study design.
Results: A majority of the research supports the view that physical fitness, single bouts of PA, and PA interventions benefit children’s cognitive functioning. Limited evidence was available concerning the effects of PA on learning, with only one cross-sectional study meeting the inclusion criteria. Evidence indicates that PA has a relationship to areas of the brain that support complex cognitive processes during laboratory tasks. Although favorable results have been obtained from cross-sectional and longitudinal studies related to academic achievement, the results obtained from controlled experiments evaluating the benefits of PA on academic performance are mixed, and additional, well-designed studies are needed.
Limitations: Limitations in evidence meeting inclusion criteria for this review include lack of randomized controlled trials, limited studies that are adequately powered, lack of information on participant characteristics, failure to blind for outcome measures, proximity of PA to measurement outcomes, and lack of accountability for known confounders. Therefore, many studies were ranked as high risk for bias because of multiple design limitations.
Conclusions: The present systematic review found evidence to suggest that there are positive associations among PA, fitness, cognition, and academic achievement. However, the findings are inconsistent, and the effects of numerous elements of PA on cognition remain to be explored, such as type, amount, frequency, and timing. Many questions remain regarding how to best incorporate PA within schools, such as activity breaks versus active lessons in relation to improved academic achievement. Regardless, the literature suggests no indication that increases in PA negatively affect cognition or academic achievement and PA is important for growth and development and general health. On the basis of the evidence available, the authors concluded that PA has a positive influence on cognition as well as brain structure and function; however, more research is necessary to determine mechanisms and long-term effect as well as strategies to translate laboratory findings to the school environment. Therefore, the evidence category rating is B. The literature suggests that PA and PE have a neutral effect on academic achievement. Thus, because of the limitations in the literature and the current information available, the evidence category rating for academic achievement is C.]]>Wed, 01 Jun 2016 00:00:00 GMT-05:0000005768-201606000-00027http://journals.lww.com/acsm-msse/Fulltext/2016/12000/Frequency_of_Breaks_in_Sedentary_Time_and.18.aspx
Purpose: To compare the metabolic effects of breaking up sedentary time with prolonged periods of standing versus multiple shorter standing bouts with the same total duration to determine whether, in principle, altering the frequency of “standing breaks” in sedentary time, influences metabolic responses over the course of the day.
Methods: Ten normoglycemic overweight/obese men (age, 33 ± 13 yr; body mass index, 28.3 ± 3.0 kg·m−2; mean ± SD) each participated in three experimental trials in random order, in which they arrived fasted, then consumed a test breakfast (8 kcal·kg−1 body weight, with 37% energy from fat, 49% from carbohydrates, 14% from protein) and, 4 h later, an identical test lunch. Expired air and blood samples were taken fasted and for 8 h postprandially. In one trial (uninterrupted sitting), participants sat continuously throughout the observation period; in the prolonged standing (PRO-Stand) trial, participants stood still for 15 min every 30 min; and in the intermittent standing trial (INT-Stand), they stood for 1.5 min, 10 times every 30 min.
Results: Compared with uninterrupted sitting, energy expenditure was 320 ± 62 kJ (10.7% ± 2.0%) higher in PRO-Stand and 617 ± 76 kJ (20.4% ± 2.3%) higher in INT-Stand: energy expenditure in INT-Stand was 296 ± 78 kJ (9.0% ± 2.3%) higher than PRO-Stand (mean ± SEM; all P < 0.001). However, there were no significant differences between trials in postprandial glucose, insulin, or triglyceride responses.
Conclusions: These data demonstrate an independent effect of frequency of sedentary breaks on energy expenditure which provides an explanation for the association between frequency of sedentary breaks and adiposity observed in epidemiological data. However, it may be necessary to break up sitting with activities of greater intensity than quiet standing to positively influence glucose, insulin, and triglyceride metabolism in relatively young, normoglycemic, overweight/obese men.]]>Thu, 01 Dec 2016 00:00:00 GMT-06:0000005768-201612000-00018http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Fitness_Moderates_the_Relationship_between_Stress.1.aspx
Purpose: This cross-sectional observational study examined the degree to which cardiorespiratory fitness (CRF) and self-perceived stress are associated with cardiometabolic risk factors and the overall risk score for cardiovascular diseases. The second aim was to determine whether participants’ CRF levels moderate the relationships between stress and cardiometabolic risk.
Methods: A gender-matched stratified sample (N = 197, 51% men, Mage = 39.2 yr) was used to ensure that participants with varying stress levels were equally represented. CRF was assessed with the Åstrand bicycle test, and perceived stress was assessed with a single-item question. Systolic blood pressure (SBP) and diastolic blood pressure (DBP), body mass index (BMI), total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), glycated hemoglobin, and total cardiometabolic risk score (sum of the z-standardized residuals of the previously mentioned indicators) were assessed as outcomes.
Results: Higher LDL-C, TG, and total metabolic risk were found in participants with high stress scores (P < 0.05). In addition, lower SBP, DBP, BMI, LDL-C, TG, and total metabolic risk were observed in participants with high CRF (P < 0.05). Two-way ANCOVA provided significant interaction effects for five of the nine outcome variables (P < 0.05, 3.6%–4.8% of explained variance). Participants with high stress who also had high CRF levels had lower SBP, DBP, LDL-C, TG, and total cardiometabolic risk than participants with high stress but low or moderate CRF levels. No significant main or interaction effects occurred for BMI, total cholesterol, high-density lipoprotein cholesterol, and glycated hemoglobin.
Conclusion: Better CRF is associated with more favorable levels of several cardiometabolic risk factors, specifically in participants experiencing high stress. Higher CRF may provide some protection against the health hazards of high chronic stress by attenuating the stress-related increase in cardiovascular risk factors.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00001http://journals.lww.com/acsm-msse/Fulltext/2016/12000/Acute_Effects_of_Low_Load_High_Repetition.2.aspx
Exercising small muscle groups at a time allows higher muscle specific workloads compared with whole body aerobic exercises in people with chronic obstructive pulmonary disease (COPD). Whether similar effects also occur with partitioning exercise during low load/high-repetition resistance exercises is uncertain.
Purpose: To investigate the acute effects of partitioning exercise on exercise workload, exertional symptoms and quadriceps muscle fatigue during low load/high-repetition resistance exercises in people with COPD and healthy controls.
Methods: We compared the acute physiological effects of single-limb (SL) versus two-limb (TL) execution of isokinetic knee extension and of six low load/high-repetition elastic resistance exercises in 20 people with COPD (forced expiratory volume in 1 s = 38% predicted) and 15 healthy controls.
Results: Among people with COPD, SL exercises resulted in higher exercise workloads during isokinetic knee extension (17% ± 31%, P < 0.05) and elastic exercises (rowing, 17% ± 23%; leg curl, 23% ± 21%; elbow flexion, 19% ± 26%; chest press, 14% ± 15%; shoulder flexion, 33% ± 24%; and knee extension, 24% ± 18%, all P < 0.05). Muscle fatigue ratings were similar during SL compared with TL exercises, whereas dyspnea ratings were similar between conditions during isokinetic exercises and lower during SL compared with TL elastic exercises (P < 0.05). In COPD, SL knee extension resulted in greater quadriceps fatigue than TL knee extension as evidenced by a greater fall in quadriceps potentiated twitch force after the former exercise (−24% ± 10% vs −16% ± 8%, P = 0.025). In healthy controls, partitioning exercise with SL exercise did not modify workload, quadriceps fatigue nor dyspnea achieved during the various exercises.
Conclusions: Partitioning exercise by exercising using an SL allowed higher muscle localized exercise workloads, larger amount of quadriceps muscle fatigue with lower, or similar level of exertional symptoms during low load/high-repetition resistance exercises in people with advanced COPD.]]>Thu, 01 Dec 2016 00:00:00 GMT-06:0000005768-201612000-00002http://journals.lww.com/acsm-msse/Fulltext/2016/11000/The_Effect_of_Different_High_Intensity.12.aspx
Purpose: This study aimed to compare the effects of three different high-intensity training (HIT) models, balanced for total load but differing in training plan progression, on endurance adaptations.
Methods: Sixty-three cyclists (peak oxygen uptake (V˙O2peak) 61.3 ± 5.8 mL·kg−1·min−1) were randomized to three training groups and instructed to follow a 12-wk training program consisting of 24 interval sessions, a high volume of low-intensity training, and laboratory testing. The increasing HIT group (n = 23) performed interval training as 4 × 16 min in weeks 1–4, 4 × 8 min in weeks 5–8, and 4 × 4 min in weeks 9–12. The decreasing HIT group (n = 20) performed interval sessions in the opposite mesocycle order as the increasing HIT group, and the mixed HIT group (n = 20) performed the interval prescriptions in a mixed distribution in all mesocycles. Interval sessions were prescribed as maximal session efforts and executed at mean values 4.7, 9.2, and 12.7 mmol·L−1 blood lactate in 4 × 16-, 4 × 8-, and 4 × 4-min sessions, respectively (P < 0.001). Pre- and postintervention, cyclists were tested for mean power during a 40-min all-out trial, peak power output during incremental testing to exhaustion, V˙O2peak, and power at 4 mmol·L−1 lactate.
Results: All groups improved 5%–10% in mean power during a 40-min all-out trial, peak power output, and V˙O2peak postintervention (P < 0.05), but no adaptation differences emerged among the three training groups (P > 0.05). Further, an individual response analysis indicated similar likelihood of large, moderate, or nonresponses, respectively, in response to each training group (P > 0.05).
Conclusions: This study suggests that organizing different interval sessions in a specific periodized mesocycle order or in a mixed distribution during a 12-wk training period has little or no effect on training adaptation when the overall training load is the same.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00012http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Acidosis_Is_Not_a_Significant_Cause_of_Skeletal.31.aspx
No abstract available]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00031http://journals.lww.com/acsm-msse/Fulltext/2016/12000/Resistance_Exercise_Augments_Postprandial.21.aspx
Introduction: We have previously shown that protein ingestion before sleep increases overnight muscle protein synthesis rates. Whether prior exercise further augments the muscle protein synthetic response to presleep protein ingestion remains to be established.
Objective: This study aimed to assess whether resistance-type exercise performed in the evening increases the overnight muscle protein synthetic response to presleep protein ingestion.
Methods: Twenty-four healthy young men were randomly assigned to ingest 30 g intrinsically L-[1-13C]-phenylalanine and L-[1-13C]-leucine-labeled casein protein before going to sleep with (PRO + EX, n = 12) or without (PRO, n = 12) prior resistance-type exercise performed in the evening. Continuous intravenous L-[ring-2H5]-phenylalanine, L-[1-13C]-leucine, and L-[ring-2H2]-tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole-body protein balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into de novo myofibrillar protein.
Results: A total of 57% ± 1% of the ingested protein-derived phenylalanine appeared in the circulation during overnight sleep. Overnight myofibrillar protein synthesis rates were 37% (0.055%·h−1 ± 0.002%·h−1 vs. 0.040%·h−1 ± 0.003%·h−1, P < 0.001, based on L-[ring-2 H5]-phenylalanine) and 31% (0.073%·h−1 ± 0.004%·h−1 vs. 0.055%·h−1 ± 0.006%·h−1, P = 0.024, based on L-[1-13C]-leucine) higher in PRO + EX compared with PRO. Substantially more of the dietary protein-derived amino acids were incorporated into de novo myofibrillar protein during overnight sleep in PRO + EX compared with PRO (0.026 ± 0.003 vs. 0.015 ± 0.003 molar percent excess, P = 0.012).
Conclusions: Resistance-type exercise performed in the evening augments the overnight muscle protein synthetic response to presleep protein ingestion and allows more of the ingested protein-derived amino acids to be used for de novo myofibrillar protein synthesis during overnight sleep.]]>Thu, 01 Dec 2016 00:00:00 GMT-06:0000005768-201612000-00021http://journals.lww.com/acsm-msse/Fulltext/2016/10000/Fitness_during_Breast_Cancer_Treatment_and.5.aspx
Purpose: This is a case study of an aerobically trained, multisport, female athlete (age = 39) diagnosed with stage IIIc human epidermal growth factor receptor 2 positive breast cancer. The focus of the study is on measures of cardiorespiratory fitness (V˙O2peak) through the course of cancer therapy.
Methods: A symptom-limited cardiopulmonary exercise tolerance test was performed to determine V˙O2peak. The tests were performed at five different time points: 1) at diagnosis of breast cancer and before initiating chemotherapy, 2) after completion of chemotherapy (5 months postdiagnosis), 3) 2.5 months after bilateral mastectomy surgery (9 months postdiagnosis), 4) immediately after radiation therapy (11 months postdiagnosis), and 5) recovery (32 months postdiagnosis).
Results: At diagnosis and before initiating chemotherapy, V˙O2peak was 50.1 mL O2·min−1·kg−1. The most precipitous decline in fitness, approximately 14%, was observed from initial diagnosis through the completion of chemotherapy. The subject regained 9% of her fitness after chemotherapy, despite an intervening mastectomy surgery. Radiation therapy was associated with an approximately 4% decline in fitness from her postmastectomy surgery value. Ultimately, 32 months after diagnosis and 22 months after the completion of radiation therapy, the subject was able to regain pretreatment fitness levels.
Conclusion: The results of the case study describe the effects of undergoing extensive breast cancer therapy on measures of V˙O2peak for a highly aerobically trained, multisport athlete. In this case, exercise training reversed the decrement in measured V˙O2peak that occurred during cancer therapy.]]>Sat, 01 Oct 2016 00:00:00 GMT-05:0000005768-201610000-00005http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Altered_Running_Economy_Directly_Translates_to.13.aspx
Purpose: Our goal was to quantify if small (1%–3%) changes in running economy quantitatively affect distance-running performance. Based on the linear relationship between metabolic rate and running velocity and on earlier observations that added shoe mass increases metabolic rate by ~1% per 100 g per shoe, we hypothesized that adding 100 and 300 g per shoe would slow 3000-m time-trial performance by 1% and 3%, respectively.
Methods: Eighteen male sub-20-min 5-km runners completed treadmill testing, and three 3000-m time trials wearing control shoes and identical shoes with 100 and 300 g of discreetly added mass. We measured rates of oxygen consumption and carbon dioxide production and calculated metabolic rates for the treadmill tests, and we recorded overall running time for the time trials.
Results: Adding mass to the shoes significantly increased metabolic rate at 3.5 m·s−1 by 1.11% per 100 g per shoe (95% confidence interval = 0.88%–1.35%). While wearing the control shoes, participants ran the 3000-m time trial in 626.1 ± 55.6 s. Times averaged 0.65% ± 1.36% and 2.37% ± 2.09% slower for the +100-g and +300-g shoes, respectively (P < 0.001). On the basis of a linear fit of all the data, 3000-m time increased 0.78% per added 100 g per shoe (95% confidence interval = 0.52%–1.04%).
Conclusion: Adding shoe mass predictably degrades running economy and slows 3000-m time-trial performance proportionally. Our data demonstrate that laboratory-based running economy measurements can accurately predict changes in distance-running race performance due to shoe modifications.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00013http://journals.lww.com/acsm-msse/Fulltext/2016/03000/Appetite_and_Energy_Intake_Responses_to_Acute.10.aspx
Purpose: To explore whether compensatory responses to acute energy deficits induced by exercise or diet differ by sex.
Methods: In experiment one, 12 healthy women completed three 9-h trials (control, exercise-induced (Ex-Def) and food restriction–induced energy deficit (Food-Def)) with identical energy deficits being imposed in the Ex-Def (90-min run, ∼70% of V˙O2max) and Food-Def trials. In experiment two, 10 men and 10 women completed two 7-h trials (control and exercise). Sixty minutes of running (∼70% of V˙O2max) was performed at the beginning of the exercise trial. The participants rested throughout the remainder of the exercise trial and during the control trial. Appetite ratings, plasma concentrations of gut hormones, and ad libitum energy intake were assessed during main trials.
Results: In experiment one, an energy deficit of approximately 3500 kJ induced via food restriction increased appetite and food intake. These changes corresponded with heightened concentrations of plasma acylated ghrelin and lower peptide YY3–36. None of these compensatory responses were apparent when an equivalent energy deficit was induced by exercise. In experiment two, appetite ratings and plasma acylated ghrelin concentrations were lower in exercise than in control, but energy intake did not differ between trials. The appetite, acylated ghrelin, and energy intake response to exercise did not differ between men and women.
Conclusions: Women exhibit compensatory appetite, gut hormone, and food intake responses to acute energy restriction but not in response to an acute bout of exercise. Additionally, men and women seem to exhibit similar acylated ghrelin and PYY3–36 responses to exercise-induced energy deficits. These findings advance understanding regarding the interaction between exercise and energy homeostasis in women.]]>Tue, 01 Mar 2016 00:00:00 GMT-06:0000005768-201603000-00010http://journals.lww.com/acsm-msse/Fulltext/2016/11000/The_Role_of_Acidosis_in_Fatigue___Pro_Perspective.30.aspx
No abstract available]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00030http://journals.lww.com/acsm-msse/Fulltext/2016/11000/The_Basic_Science_of_Exercise_Fatigue.19.aspx
No abstract available]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00019http://journals.lww.com/acsm-msse/Fulltext/2016/01000/Selected_Issues_in_Injury_and_Illness_Prevention.21.aspx
No abstract available]]>Fri, 01 Jan 2016 00:00:00 GMT-06:0000005768-201601000-00021http://journals.lww.com/acsm-msse/Fulltext/2016/10000/Neutrophil_Depletion_Attenuates_Muscle_Injury.8.aspx
Purpose: The infiltration of macrophages in skeletal muscle during exhaustive exercise promotes inflammation, myofiber lesion, and muscle injury. Although neutrophils upregulate macrophage infiltration in skeletal muscles during exercise, the role of neutrophils in promoting muscle injury after exhaustive exercise remains unclear. In this study, we investigated the effects of preexercise neutrophil depletion with antineutrophil antibody treatment on muscle injury, inflammation, and macrophage infiltration after exhaustive exercise.
Methods: Male C57BL/6J mice were randomly assigned to four groups, namely, sedentary with control antibody (n = 10), sedentary with antineutrophil antibody (n = 10), exhaustive exercise with control antibody (n = 10), and exhaustive exercise with antineutrophil antibody (n = 10). The mice were given intraperitoneal injection of the antineutrophil antibody (anti-Ly-6G, clone 1A8) or the control antibody (anti-Ly-6G, clone 2A3), and remained inactive or performed exhaustive exercise on a treadmill 48 h after the injection. Twenty-four hours after the exhaustive exercise, the gastrocnemius muscles were removed for histological and polymerase chain reaction (PCR) analyses. Infiltration of neutrophils and macrophages was evaluated with Ly-6G and F4/80 immunohistochemistry staining procedures. Muscle fiber injury was detected based on the number of IgG staining fiber. The mRNA expression levels of proinflammatory cytokines and chemokines were evaluated with real-time reverse transcription PCR.
Results: Exhaustive exercise increased neutrophil infiltration into the gastrocnemius muscle substantially by 3.1-fold and caused muscle injury, but these effects were markedly suppressed by preexercise treatment with antineutrophil antibody (neutrophil infiltration, 0.42-fold, and muscle injury, 0.18-fold). Treatment with antineutrophil antibody also decreased macrophage infiltration (0.44-fold) and mRNA expression of tumor necrosis factor-α (0.55-fold) and interleukin-6 (0.51-fold) in the skeletal muscle after exhaustive exercise.
Conclusion: These results suggest that neutrophils contribute to exacerbating muscle injury by regulating inflammation through the induction of macrophage infiltration.]]>Sat, 01 Oct 2016 00:00:00 GMT-05:0000005768-201610000-00008http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Resistance_Training_Increases_Skeletal_Muscle.11.aspx
Purpose: Skeletal muscle capillarization plays a key role in oxygen and nutrient delivery to muscle. The loss of muscle mass with aging and the concept of anabolic resistance have been, at least partly, attributed to changes in skeletal muscle capillary structure and function. We aimed to compare skeletal muscle capillarization between young and older men and evaluate whether resistance-type exercise training increases muscle capillarization in older men.
Methods: Muscle biopsies were obtained from the vastus lateralis of healthy young (n = 14, 26 ± 2 yr) and older (n = 16, 72 ± 1 yr) adult men, with biopsies before and after 12 wk of resistance-type exercise training in the older subjects. Immunohistochemistry was used to assess skeletal muscle fiber size, capillary contacts (CC) per muscle fiber, and the capillary-to-fiber perimeter exchange (CFPE) index in type I and II muscle fibers.
Results: Type II muscle fibers were smaller in old versus young (4507 ± 268 vs 6084 ± 497 μm2, respectively, P = 0.007). Type I and type II muscle fiber CC and CFPE index were smaller in old compared with young muscle (CC type I: 3.8 ± 0.2 vs 5.0 ± 0.3; CC type II: 3.2 ± 0.2 vs 4.2 ± 0.2, respectively; both P < 0.001). Resistance-type exercise training increased type II muscle fiber size only. In addition, CC and CFPE index increased in both the type I (26% ± 9% and 27% ± 8%) and type II muscle fibers (33% ± 7% and 24% ± 6%, respectively; all P ≤ 0.001) after 12 wk resistance training in older men.
Conclusions: We conclude that resistance-type exercise training can effectively augment skeletal muscle fiber capillarization in older men. The greater capillary supply may be an important prerequisite to reverse anabolic resistance and support muscle hypertrophy during lifestyle interventions aiming to support healthy aging.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00011http://journals.lww.com/acsm-msse/Fulltext/2016/09000/Leisure_Time_Physical_Activity_and_the_Risk_of.13.aspx
Introduction: The risk of upper respiratory tract viral infections is reduced with increased physical activity, but little information is available regarding bacterial infections. We examined the relationship between leisure-time physical activity and suspected bacterial infections.
Methods: Information on leisure-time physical activity was obtained from the 2007 and 2010 North Denmark Region Health Surveys of 18,874 Danes and linked to data from nationwide administrative registries. Suspected bacterial infections were determined based on filled prescriptions for antibiotics. Adjusted estimates were calculated using logistic regression models.
Results: During a 1-yr follow-up, 5368 participants filled at least one antibiotic prescription. There was a statistically significant difference between physical activity level and filling any antibiotic prescriptions among women (P = 0.003) but not among men (P = 0.191). Logistic regression analysis showed that compared with sedentary behavior, all levels of leisure-time physical activities lowered the likelihood of filling an antibiotic prescription. However, after multivariable adjustments, only estimates of low physical activity were significant (odds ratio [OR] = 0.90, 95% confidence interval [CI] = 0.82; 0.99). Multivariable adjusted subgroup analyses of suspected cystitis showed a decreased likelihood of engaging in low (OR = 0.79, 95% CI = 0.65–0.95) and moderate (OR = 0.68, 95% CI = 0.54–0.87) physical activity.
Conclusion: Low leisure-time physical activity is associated with a statistically significant 10% lower risk of suspected bacterial infections during a 1-yr follow-up compared with sedentary behavior. Further, low and moderate levels of physical activity were associated with the statistically significant reduction of suspected cystitis. No reduction in suspected respiratory tract infections was statistically significant and associated with physical activity compared with sedentary behavior.]]>Thu, 01 Sep 2016 00:00:00 GMT-05:0000005768-201609000-00013http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Neural_Contributions_to_Muscle_Fatigue___From_the.27.aspx
During exercise, there is a progressive reduction in the ability to produce muscle force. Processes within the nervous system as well as within the muscles contribute to this fatigue. In addition to impaired function of the motor system, sensations associated with fatigue and impairment of homeostasis can contribute to the impairment of performance during exercise. This review discusses some of the neural changes that accompany exercise and the development of fatigue. The role of brain monoaminergic neurotransmitter systems in whole-body endurance performance is discussed, particularly with regard to exercise in hot environments. Next, fatigue-related alterations in the neuromuscular pathway are discussed in terms of changes in motor unit firing, motoneuron excitability, and motor cortical excitability. These changes have mostly been investigated during single-limb isometric contractions. Finally, the small-diameter muscle afferents that increase firing with exercise and fatigue are discussed. These afferents have roles in cardiovascular and respiratory responses to exercise, and in the impairment of exercise performance through interaction with the motor pathway, as well as in providing sensations of muscle discomfort. Thus, changes at all levels of the nervous system, including the brain, spinal cord, motor output, sensory input, and autonomic function, occur during exercise and fatigue. The mix of influences and the importance of their contribution vary with the type of exercise being performed.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00027http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Fatigue___Where_Did_We_Come_from_and_How_Did_We.20.aspx
This paper highlights some key concepts related to fatigue and the seminal role of the 1981 Ciba Foundation Symposia “Human Muscle Fatigue: Physiological Mechanisms” chaired by R.H.T. Edwards in consolidating key ideas that have moved the study of fatigue forward since that time. I also consider these concepts in their historical context via the pioneering work of the Italian physiologist and social activist Angelo Mosso in the late 1800s. Finally, fatigue as a multidimensional concept with implications beyond muscle physiology is considered.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00020http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Postexercise_High_Fat_Feeding_Suppresses_p70S6K1.5.aspx
Purpose: This study aimed to examine the effects of reduced CHO but high postexercise fat availability on cell signaling and expression of genes with putative roles in regulation of mitochondrial biogenesis, lipid metabolism, and muscle protein synthesis.
Methods: Ten males completed a twice per day exercise model (3.5 h between sessions) comprising morning high-intensity interval training (8 × 5 min at 85% V˙O2peak) and afternoon steady-state (SS) running (60 min at 70% V˙O2peak). In a repeated-measures design, runners exercised under different isoenergetic dietary conditions consisting of high-CHO (HCHO: 10 g·kg−1 CHO, 2.5 g·kg−1 protein, and 0.8 g·kg−1 fat for the entire trial period) or reduced-CHO but high-fat availability in the postexercise recovery periods (HFAT: 2.5 g·kg−1 CHO, 2.5 g·kg−1 protein, and 3.5 g·kg−1 fat for the entire trial period).
Results: Muscle glycogen was lower (P < 0.05) at 3 h (251 vs 301 mmol·kg−1 dry weight) and 15 h (182 vs 312 mmol·kg−1 dry weight) post-SS exercise in HFAT compared with HCHO. Adenosine monophosphate-activated protein kinase α2 activity was not increased post-SS in either condition (P = 0.41), although comparable increases (all P < 0.05) in PGC-1α, p53, citrate synthase, Tfam, peroxisome proliferator-activated receptor, and estrogen-related receptor α mRNA were observed in HCHO and HFAT. By contrast, PDK4 (P = 0.003), CD36 (P = 0.05), and carnitine palmitoyltransferase 1 (P = 0.03) mRNA were greater in HFAT in the recovery period from SS exercise compared with HCHO. Ribosomal protein S6 kinase activity was higher (P = 0.08) at 3 h post-SS exercise in HCHO versus HFAT (72.7 ± 51.9 vs 44.7 ± 27 fmol·min−1·mg−1).
Conclusion: Postexercise high-fat feeding does not augment the mRNA expression of genes associated with regulatory roles in mitochondrial biogenesis, although it does increase lipid gene expression. However, postexercise ribosomal protein S6 kinase 1 activity is reduced under conditions of high-fat feeding, thus potentially impairing skeletal muscle remodeling processes.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00005http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Association_between_Lower_Extremity_Muscle.2.aspx
Purpose: This study aimed to prospectively investigate the association between isolated and functional lower extremity muscle strength and the risk for noncontact anterior cruciate ligament (ACL) injury in Norwegian female elite handball and football players.
Methods: From 2007 through 2015, premier league players participated in strength testing and were prospectively followed for ACL injury risk. At baseline, we recorded player demographics, playing and ACL injury history, and measured peak concentric isokinetic quadriceps and hamstring torques (60°·s−1), hamstring-to-quadriceps ratio, isometric hip abduction strength, and one-repetition maximum in a seated leg press. We followed a predefined statistical protocol where we generated five separate logistic regression models, one for each of the proposed strength risk factors and adjusted for confounding factors. New ACL injury was the outcome, using the leg as the unit of analysis.
Results: A total of 57 (6.6%) of 867 players (age = 21 ± 4 yr, height = 170 ± 6 cm, body mass = 66 ± 8 kg) suffered from a noncontact ACL injury after baseline testing (1.8 ± 1.8 yr). The OR of sustaining a new injury among those with an ACL injury history was 3.1 (95% confidence interval = 1.6–6.1). None of the five strength variables selected were statistically associated with an increased risk of ACL rupture when adjusted for sport, dominant leg, ACL injury history, and height.
Conclusion: Peak lower extremity strength was not associated with an increased ACL injury risk among female elite handball and football players. Hence, peak strength, as measured in the present study, cannot be used to screen elite female athletes to predict injury risk.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00002http://journals.lww.com/acsm-msse/Fulltext/2013/12000/Selected_Issues_for_Nutrition_and_the_Athlete___A.21.aspx
No abstract available]]>Sun, 01 Dec 2013 00:00:00 GMT-06:0000005768-201312000-00021http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Translating_Fatigue_to_Human_Performance.21.aspx
ABSTRACT: Despite flourishing interest in the topic of fatigue—as indicated by the many presentations on fatigue at the 2015 Annual Meeting of the American College of Sports Medicine—surprisingly little is known about its effect on human performance. There are two main reasons for this dilemma: 1) the inability of current terminology to accommodate the scope of the conditions ascribed to fatigue, and 2) a paucity of validated experimental models. In contrast to current practice, a case is made for a unified definition of fatigue to facilitate its management in health and disease. On the basis of the classic two-domain concept of Mosso, fatigue is defined as a disabling symptom in which physical and cognitive function is limited by interactions between performance fatigability and perceived fatigability. As a symptom, fatigue can only be measured by self-report, quantified as either a trait characteristic or a state variable. One consequence of such a definition is that the word fatigue should not be preceded by an adjective (e.g., central, mental, muscle, peripheral, and supraspinal) to suggest the locus of the changes responsible for an observed level of fatigue. Rather, mechanistic studies should be performed with validated experimental models to identify the changes responsible for the reported fatigue. As indicated by three examples (walking endurance in old adults, time trials by endurance athletes, and fatigue in persons with multiple sclerosis) discussed in the review, however, it has proven challenging to develop valid experimental models of fatigue. The proposed framework provides a foundation to address the many gaps in knowledge of how laboratory measures of fatigue and fatigability affect real-world performance.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00021http://journals.lww.com/acsm-msse/Fulltext/2012/05002/Abst_D_FreeCommPosters.5.aspx
No abstract available]]>Tue, 01 May 2012 00:00:00 GMT-05:0000005768-201205002-00005http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Walking_and_Running_Require_Greater_Effort_from.14.aspx
Introduction: The knee and ankle extensors as human primary antigravity muscle groups are of utmost importance in a wide range of locomotor activities. Yet, we know surprisingly little about how these muscle groups work, and specifically, how close to their maximal capacities they function across different modes and intensity of locomotion. Therefore, to advance our understanding of locomotor constraints, we determined and compared relative operating efforts of the knee and ankle extensors during walking, running, and sprinting.
Methods: Using an inverse dynamics biomechanical analysis, the muscle forces of the knee and ankle extensors during walking (1.6 m·s−1), running (4.1 m·s−1), and sprinting (9.3 m·s−1) were quantified and then related to maximum forces of the same muscle groups obtained from a reference hopping test that permitted natural elastic limb behavior.
Results: During walking, the relative effort of the ankle extensors was almost two times greater compared with the knee extensors (35% ± 6% vs 19% ± 5%, P < 0.001). Changing walking to running decreased the difference in the relative effort between the extensor muscle groups, but still, the ankle extensors operated at a 25% greater level than the knee extensors (84% ± 12% vs 63% ± 17%, P < 0.05). At top speed sprinting, the ankle extensors reached their maximum operating level, whereas the knee extensors still worked well below their limits, showing a 25% lower relative effort compared with the ankle extensors (96% ± 11% vs 72% ± 19%, P < 0.01).
Conclusions: Regardless of the mode of locomotion, humans operate at a much greater relative effort at the ankle than knee extensor muscles. As a consequence, the great demand on ankle extensors may be a key biomechanical factor limiting our locomotor ability and influencing the way we locomote and adapt to accommodate compromised neuromuscular system function.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00014http://journals.lww.com/acsm-msse/Fulltext/2016/06000/Physical_Activity,_Fitness,_Cognitive_Function,.28.aspx
No abstract available]]>Wed, 01 Jun 2016 00:00:00 GMT-05:0000005768-201606000-00028http://journals.lww.com/acsm-msse/Fulltext/2015/05000/Music_Enhances_Performance_and_Perceived_Enjoyment.21.aspx
Introduction: Interval exercise training can elicit physiological adaptations similar to those of traditional endurance training, but with reduced time. However, the intense nature of specific protocols, particularly the “all-out” efforts characteristic of sprint interval training (SIT), may be perceived as being aversive. The purpose of this study was to determine whether listening to self-selected music can reduce the potential aversiveness of an acute session of SIT by improving affect, motivation, and enjoyment, and to examine the effects of music on performance.
Methods: Twenty moderately active adults (22 ± 4 yr) unfamiliar with interval exercise completed an acute session of SIT under two different conditions: music and no music. The exercise consisted of four 30-s “all-out” Wingate Anaerobic Test bouts on a cycle ergometer, separated by 4 min of rest. Peak and mean power output, RPE, affect, task motivation, and perceived enjoyment of the exercise were measured. Mixed-effects models were used to evaluate changes in dependent measures over time and between the two conditions.
Results: Peak and mean power over the course of the exercise session were higher in the music condition (coefficient = 49.72 [SE = 13.55] and coefficient = 23.65 [SE = 11.30]; P < 0.05). A significant time by condition effect emerged for peak power (coefficient = −12.31 [SE = 4.95]; P < 0.05). There were no between-condition differences in RPE, affect, or task motivation. Perceived enjoyment increased over time and was consistently higher in the music condition (coefficient = 7.00 [SE = 3.05]; P < 0.05).
Conclusion: Music enhances in-task performance and enjoyment of an acute bout of SIT. Listening to music during intense interval exercise may be an effective strategy for facilitating participation in, and adherence to, this form of training.]]>Fri, 01 May 2015 00:00:00 GMT-05:0000005768-201505000-00021http://journals.lww.com/acsm-msse/Fulltext/2015/11000/Concussion_Frequency_Associates_with.15.aspx
Objective: Concussion is commonly associated with immediate and persistent alterations in motor function affecting postural control and gait. Patients with lower extremity joint injury have demonstrated functional alterations in the cerebral cortex, suggesting that musculoskeletal injury may be linked to alterations in brain function. Therefore, we examined the associations between concussion frequency and lower extremity musculoskeletal injury sustained during professional careers of National Football League (NFL) players in a cross-sectional study.
Methods: An inclusive health history survey was mailed to 3647 NFL players who retired during 1930–2001. Respondents reported total concussion frequency (zero, one, two, or three or more) and presence (yes/no) of specific knee and ankle musculoskeletal injury during their NFL career. Separate logistic regression models were used to estimate associations between concussion frequency and each musculoskeletal injury type, adjusting for number of years played in the NFL, body mass index while playing in the NFL, and playing position.
Results: Data from 2429 players (66.6% response rate) were available for analysis. Nearly 61% reported experiencing a concussion while competing in the NFL. Meniscal tear was the most commonly reported musculoskeletal injury (32%). Compared with NFL players who did not sustain a concussion, retired NFL players with one, two, or three or more concussions had between 18% and 63%, 15% and 126%, and 73% and 165% higher odds of reporting various musculoskeletal injuries, respectively.
Conclusions: A history of concussions was associated with a history of musculoskeletal injuries during NFL careers. These data suggest that a higher number of concussions is linked with higher odds of reporting a musculoskeletal injury.]]>Sun, 01 Nov 2015 00:00:00 GMT-05:0000005768-201511000-00015http://journals.lww.com/acsm-msse/Fulltext/2016/11000/Critical_Power___An_Important_Fatigue_Threshold_in.29.aspx
The hyperbolic form of the power–duration relationship is rigorous and highly conserved across species, forms of exercise, and individual muscles/muscle groups. For modalities such as cycling, the relationship resolves to two parameters, the asymptote for power (critical power [CP]) and the so-called W′ (work doable above CP), which together predict the tolerable duration of exercise above CP. Crucially, the CP concept integrates sentinel physiological profiles—respiratory, metabolic, and contractile—within a coherent framework that has great scientific and practical utility. Rather than calibrating equivalent exercise intensities relative to metabolically distant parameters such as the lactate threshold or V˙O2max, setting the exercise intensity relative to CP unifies the profile of systemic and intramuscular responses and, if greater than CP, predicts the tolerable duration of exercise until W′ is expended, V˙O2max is attained, and intolerance is manifested. CP may be regarded as a “fatigue threshold” in the sense that it separates exercise intensity domains within which the physiological responses to exercise can (CP) be stabilized. The CP concept therefore enables important insights into 1) the principal loci of fatigue development (central vs. peripheral) at different intensities of exercise and 2) mechanisms of cardiovascular and metabolic control and their modulation by factors such as O2 delivery. Practically, the CP concept has great potential application in optimizing athletic training programs and performance as well as improving the life quality for individuals enduring chronic disease.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00029http://journals.lww.com/acsm-msse/Fulltext/2013/01000/Prevention,_Diagnosis,_and_Treatment_of_the.27.aspx
No abstract available]]>Tue, 01 Jan 2013 00:00:00 GMT-06:0000005768-201301000-00027http://journals.lww.com/acsm-msse/Fulltext/2016/11000/No_Muscle_Is_an_Island___Integrative_Perspectives.26.aspx
ABSTRACT: Muscle fatigue has been studied with a variety approaches, tools and technologies. The foci of these studies have ranged tremendously, from molecules to the entire organism. Single cell and animal models have been used to gain mechanistic insight into the fatigue process. The theme of this review is the concept that the mechanisms of muscle fatigue do not occur in isolation in vivo: muscular work is supported by many complex physiological systems, any of which could fail during exercise and thus contribute to fatigue. To advance our overall understanding of fatigue, a combination of models and approaches is necessary. In this review, we examine the roles that neuromuscular properties, intracellular glycogen, oxygen metabolism, and blood flow play in the fatigue process during exercise and pathological conditions.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00026http://journals.lww.com/acsm-msse/Fulltext/2016/11000/The_Relevance_of_Sex_Differences_in_Performance.23.aspx
ABSTRACT: Performance fatigability differs between men and women for a range of fatiguing tasks. Women are usually less fatigable than men, and this is most widely described for isometric fatiguing contractions and some dynamic tasks. The sex difference in fatigability is specific to the task demands so that one mechanism is not universal, including any sex differences in skeletal muscle physiology, muscle perfusion, and voluntary activation. However, there are substantial knowledge gaps about the task dependency of the sex differences in fatigability, the involved mechanisms, and the relevance to clinical populations and with advanced age. The knowledge gaps are in part due to the significant deficits in the number of women included in performance fatigability studies despite a gradual increase in the inclusion of women for the last 20 yr. Therefore, this review 1) provides a rationale for the limited knowledge about sex differences in performance fatigability, 2) summarizes the current knowledge on sex differences in fatigability and the potential mechanisms across a range of tasks, 3) highlights emerging areas of opportunity in clinical populations, and 4) suggests strategies to close the knowledge gap and understanding the relevance of sex differences in performance fatigability. The limited understanding about sex differences in fatigability in healthy and clinical populations presents as a field ripe with opportunity for high-impact studies. Such studies will inform on the limitations of men and women during athletic endeavors, ergonomic tasks, and daily activities. Because fatigability is required for effective neuromuscular adaptation, sex differences in fatigability studies will also inform on optimal strategies for training and rehabilitation in both men and women.]]>Tue, 01 Nov 2016 00:00:00 GMT-05:0000005768-201611000-00023http://journals.lww.com/acsm-msse/Fulltext/2012/12000/The_Team_Physician_and_the_Return_to_Play.25.aspx
No abstract available]]>Sat, 01 Dec 2012 00:00:00 GMT-06:0000005768-201212000-00025http://journals.lww.com/acsm-msse/Fulltext/2015/02000/The_Team_Physician_and_Strength_and_Conditioning.27.aspx
No abstract available]]>Sun, 01 Feb 2015 00:00:00 GMT-06:0000005768-201502000-00027